Hopefully I have indicated what black holes are, some of their properties and
why we believe they exist.
Why are they important, apart from providing material for Star Trek episodes, and
in particular, why I am spending a great deal of time studying them theoretically?
Stephen Hawking showed in the mid-seventies that black holes aren't black. They
glow in the dark like very faint light bulbs. They emit radiation via microscopic
processes that occur just outside the horizon. The net effect is to remove energy
from the black hole, although at a very, very slow rate. Thus black holes
ultimately evaporate. In reality, a solar mass black hole will take many many times
the lifetime of the Universe to evaporate, so who cares?
This process gives rise to two related fundamental theoretical problem:
the problem of information loss and the mysterious source of black hole entropy.
The first is a bit easier to visualize, so I will describe that.